Scroll to see break-even price per barrel for oil in 2015 for select oil producers, and click on a country's name for more details. modest oil-price recovery and currency devaluations have lowered breakeven prices for countries like Russia and Nigeria, but some petrostates still need oil prices above $100 a barrel to balance their budgets.
There are dozens of types of gemstones â including diamonds, colored gemstones, and pearls â each with a unique set of physical and optical properties. GIRDLE â The narrow band around the perimeter of a polished or faceted diamond or colored gemstone.
How Gemstones are Formed. Minerals form under various conditions in the earth. Most gemstones form in the Earth's crust; the top layer of the Earth, with a depth of 3 to 25 miles. Only two gemstone varieties-diamond and peridot-form in the Earth's mantle, which represents 80% of the Earth's volume.ow Gemstones are Formed. Minerals form under various conditions in the earth. Most gemstones form in the Earth's crust; the top layer of the Earth, with a depth of 3 to 25 miles. Only two gemstone varieties-diamond and peridot-form in the Earth's mantle, which represents 80% of the Earth's volume.